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Multiple variations of extensor muscles of forearm in relation to the radial nerve: a case report and review/Multiples variaciones de los musculos extensores del antebrazo en relacion con el nervio radial: reporte de caso y revision.


Marked variations from the normal are rarely seen in superficial group of extensors (Hollinshead, 1969). Occasionally, aberrant muscle slips are present among the superficial group of extensors (Hollinshead). The course of radial nerve in the lower part of arm lies between the brachialis and the brachioradialis and extensor carpi radialis longus muscles and this position gives off the nerves to these muscles (Anson & McVay, 1971; Hollinshead). The radial tunnel is described as a 5-cm long furrow bounded by brachialis and the biceps tendon medially and the mobile extensor muscles anterolaterally, beginning just proximal to the radiocapitellar joint and ending at the distal edge of supinator. After the point of bifurcation of the radial nerve, the posterior interosseous nerve (PIN) travels through the radial tunnel (Loh et al., 2004). Prasartritha et al. (1993) dissected sixty fresh cadaveric upper extremities and suggested the course of the radial nerve in the radial tunnel, an area that varies but begins in the furrow between the brachioradialis and brachialis in the distal arm and ends at the distal edge of the supinator muscle in the proximal forearm. Ferdinand et al. (2006) concluded that the most common MRI (magnetic resonance imaging) finding in radial tunnel syndrome are muscle denervation edema or atrophy along the distribution of the PIN.


The following variations were observed on the right side during routine dissection in an adult 34 year old male cadaver. Brachialis was giving additional head of origin for brachioradialis close to its bony origin from humerus; thus making the radial nerve more vulnerable to compression proximal to and through its course in the radial tunnel (Fig. 1). Extensor carpi radialis brevis (ECRB) was absent, whereas extensor carpi radialis longus (ECRL) was giving two tendons in the second compartment of extensor retinaculum before its insertion while passing deep to the abductor pollicis longus (Fig. 2).




While dissecting the body of an 80-year-old female Claassen & Wree (2002) described variation of ECRL, which gave origin to an accessory head. The tendon of this accessory head passed through a separate tunnel in the extensor retinaculum and inserted in the middle of the first metacarpal bone (Claassen & Wree). On the contrary in the present case ECRL was passing as two tendons in the second compartment of extensor retinaculum before its insertion. Caetano et al. (2004) analyzed the anatomical variations of the ECRL and ECRB in sixty male adults cadaver upper limbs and reported that the supernumerary tendons were found in 3 hands (all in relation to the ECRL tendon), whereas the presence of an accessory tendon making the union between the tendons of ECRL and ECRB was registered in 4 dissected hands (Caetano et al.). Whereas in the present case, the ECRL received an additional head of origin from brachialis and divided into two tendons before insertion.

Sixty upper limbs from 30 Turkish subjects (18 males and 12 females) were dissected to reveal the course of the PIN and to examine possible compression sites at the proximal and distal edges of the supinator muscle, and the exit of the nerve from the ECRB (Kirici & Irmak, 2004). An anatomic study of 45 supper limbs, from 40 cadavers, was performed to analyse the relations between the medial edge of the ECRB and the PIN and Laulan et al. (1994) suggested that the ECRB is a possible cause of PIN entrapment. Hence, the absence of ECRB in our case further increased the chances of PIN entrapment

Embryological hypothesis and phylogenic correlation: In lower mammals the two extensores carpi radiales are represented by one muscle (Bergman et al., 1988). Anatomical variations always have underlying cause as developmental arrest in the different stages of gestation. Ontogeny repeats phylogeny hence, the pattern of muscular arrangement in this case can be said to be less evolved than the usual arrangement.

Received: 01-02-2007 Accepted: 12-09-2007


Anson, B. J. & McVay, C. B. Surgical Anatomy. 5th ed. W.B. Saunders Company, Philadelphia, 1971. pp.1012-7.

Bergman, R. A.; Thompson, S. A.; Afifi, A. K. & Saddeh, F. A. Copendium of Human Anatomical Variation. Urban and Schwarzenburg, Baltimore, 1988. pp.138-9.

Caetano, F. M.; Albertoni, M. W.; Caetano, B. E. & Perez, M. R. Anatomical study of insertions of the extensor carpi radialis longus and brevis. Int. J. Morphol., 22(4):24551, 2004.

Claassen, H. & Wree, A. Multiple variations in the region of Mm. extensores carpi radialis longus and brevis. Ann. Anat., 184:489-91, 2002.

Ferdinand, B. D.; Rosenberg, Z. S.; Schweitzer, M. E.; Stuchin, S. A.; Jazrawi, L. M.; Lenzo, S. R.; Meislin, R. J. & Kiprovski, K. MR imaging features of radial tunnel syndrome: initial experience. Radiology, 240:161-8, 2006.

Hollinshead, W. H. Anatomy for Surgeons. The Back and Limbs. Vol 3. 2nd Ed. Harper and Row Publishers, Newyork, 1969. pp.428-41.

Kirici, Y. & Irmak, M. K. Investigation of two possible compression sites of the deep branch of the radial nerve and nerve supply of the extensor carpi radialis brevis muscle. Neurol. Med. Chir. (Tokyo), 44:14-9, 2004.

Laulan, J.; Daaboul, J.; Fassio, E. & Favard, L. The relation of the short radial extensor muscle of the wrist with the deep branch division of the radial nerve. Its significance in the physiopathology of elbow pain. Ann. Chir. Main Memb. Super., 13:366-72, 1994.

Loh, Y. C.; Lam, W. L.; Stanley, J. K. & Soames, R. W. A new clinical test for radial tunnel syndrome-the RuleofNine test: A cadaveric study. J. Orthop. Surg. (Hong Kong), 12(1):83-6, 2004.

Prasartritha, T.; Liupolvanish, P. & Rojanakit, A. A study of the posterior interosseous nerve (PIN) and the radial tunnel in 30 Thai cadavers. J. Hand Surg. [Am], 18:10712, 1993.

Correspondence to:

Dr. Prakash

Department of Anatomy

Centre for Basic Sciences

Kasturba Medical College

Pin: 575004

Bejai, Mangalore, Karnataka


Phone: 919342321730, 918242211746 (Off.)

Fax: 918242428183


* Prakash; Rajalakshmi Rai; *Anu Vinod Ranade; *Latha V Prabhu; *Mangala M Pai & **Gajendra Singh

* Department of Anatomy, C.B.S., Kasturba Medical College, Bejai, Mangalore, Karnataka, INDIA, Pin: 575004. ** Department of Anatomy, Institute of Medical Sciences, Banaras Hindu University, Varanasi, U.P., INDIA, Pin: 221 005.
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Author:Prakash; Rai, Rajalakshmi; Ranade, Anu Vinod; Prabhu, Latha V.; Pai, Mangala M.; Singh, Gajendra
Publication:International Journal of Morphology
Date:Jun 1, 2008
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